The Prohibition era in America, which lasted for well over a decade and—inconceivable as it might be today—effectively banned the sale and production of booze in the United States, ended with the ratification of the 21st Amendment on Dec. 5, 1933.

Workers walk to a cassiterite, coltan and tourmaline mine near the town of Numbi, South Kivu, Democratic Republic of Congo. The minerals are used to make key components in electronic devices, including mobile phones.

Like many photojournalists, I’ve been shooting with my iPhone for a while. Using a mobile phone allows me to be somewhat invisible as a professional photographer; people see me as just another person in the crowd. Invisibility is particularly useful in the eastern part of the Democratic Republic of Congo, where a potpourri of armed groups and governments have used conflict minerals as the latest way to help fund the warfare, atrocities and repression that have afflicted the area for more than a century.

The electronics industry is one of the main destinations for these minerals, which include tourmaline, cassiterite and coltan. They are used to make critical components of mobile phones, laptops and other gadgets. So it is fitting—if ironic—that I shot this entire essay with my iPhone. I arrived in Congo in early August to document some of the mines in an attempt to highlight how the minerals travel out of the country—and the trade’s effect on the lives of the workers who handle them along the way. At a camp for internally displaced people in Kibati, the phone helped me shoot scenes unobtrusively. Taking photographs with a phone also raises my awareness as a photographer. Instead of concentrating on camera settings and a large piece of equipment, I am better able to focus on the situation before me. It becomes more about how I feel and what I see.

In Congo, the effects of the mineral trade on every person’s life—even the lives of people who aren’t working at the mines—are palpable. At a Heal Africa clinic in Goma, I met an emaciated teenage girl who had been gang-raped by three Hutu militiamen allegedly funded by profits from the mines. I’m not advocating giving up our gadgets. The causes of problems in Congo are far more complex. There are industry sponsored programs like Solutions for Hope, which tries to monitor coltan. But auditing the origins of these minerals is complicated by inaccessibility and danger. I’d like people to pause when they look at these photographs, taking time to think about where the material for modern technology comes from—and what lives are affected before they get into the phones in our hands.

Michael Christopher Brown is a photographer based in New York City. His photographs appear in this week’s issue of TIME. See more of his work here.